The invention relates to an apparatus for feeding fuel from a supply container to an internal combustion engine of a motor vehicle as generically defined by the preamble to claim 1.
One such apparatus is known from German Patent Disclosure DE 195 49 192. The fuel feed module described has a mushroom-shaped closing element in the bottom region of its suction container. This closing element is received in axially movable fashion. The mushroomlike part of the closing element spans an opening in the bottom of the suction container of the fuel feed module, by way of which the interior of the suction container of the fuel feed module communicates with the interior of a supply container. By its own weight, the closing element rests on the inside of the bottom of the suction container, spanning the opening, so that the opening is sealingly closed. When fuel is now introduced into the supply container, the fuel level in it rises, and as a result the static pressure acting on the underside of the closing element increases as well. This opens the valve, and fuel flows out of the supply container through the opening in the bottom of the suction container into the interior of the suction container. From the interior of the suction container, the fuel is delivered to the motor vehicle engine by means of a fuel feed module.
So that fuel can be delivered to the engine by the fuel feed unit, it is therefore necessary for relatively large quantities of fuel to be introduced into the supply container, so that an adequately high static pressure can be built up to open the closing element and thus enable the fuel to flow into the interior of the suction container. A disadvantage of an initial-fill valve actuated by the static pressure is thus the relatively large quantity of fuel that must be fed into the supply container in order to actuate the initial-fill valve.
It is therefore the object of the invention to create an apparatus for feeding fuel from a supply container to an internal combustion engine of a motor vehicle which in particular assures reliable initial filling of the fuel feed module after the final assembly of a motor vehicle the first time its tank is filled, or if the supply container has run empty, or only slight fuel quantities are present.
This object is attained by an apparatus having the characteristics of claim 1. Expedient refinements are defined by the dependent claims.
The apparatus according to the invention for feeding fuel from a supply container to an internal combustion engine of a motor vehicle. The apparatus has a fuel feed unit which on the intake side communicates with a suction container, communicating with the supply container, and on the pressure side communicates with the engine, and having a return line for feeding excess fuel into the suction container. In its bottom region the suction container has a closing element, which is movable between a first position, in which the suction container is opened relative to the supply container, and a second position, in which the suction container is closed relative to the supply container. According to the invention, the closing element has an actuating device, preferably a float body, which in particular at a low or zero fuel level in the supply container keeps the closing element in the first, open position, and which when at least enough fuel is located in the suction container so that the fuel feed unit can still furnish enough fuel to the engine, keeps the closing element in the second, closed position.
One essential advantage of a closing element having an actuating device is that the sealing function and closing function of the closing element are decoupled from one another. This kind of closing element according to the invention, also known as an initial-fill valve, is connected to the actuating device in such a way that when the tank is empty, the closing element is opened. Accordingly, for actuating the initial-fill valve, there is no need for a static pressure to be built up. As a result, even when the slightest fuel quantities are introduced, an immediate inflow of fuel from the supply container into the interior of the suction container is assured. A further advantage of a closing element embodied in this way is that when the tank is empty, the initial-fill valve is kept in the open position, so that sticking effects at the sealing seat that would otherwise occur are eliminated. Especially with an actuating device that is controlled as a function of the fuel level in the supply tank, a precisely defined closing point of the closing element is settable or attainable.
In one exemplary embodiment of the invention, the actuating device is embodied as a float body and is connected to the closing element. The closing element is attached to the bottom of the suction container of the fuel feed module in such a way that when no fuel is present, the closing element is located in the open position by its total mass, comprising the mass of the closing element itself and the mass of the float body, since in the absence of fuel the float body is not lent any buoyancy. The float body is dimensioned such that in the event that the float body is immersed in the fuel or surrounded by it, a buoyant force develops which is greater than the mass force exerted by the total mass of the closing element. As a result, the closing element is put in the closing position. The closing forces are greater, the larger the dimensions of the float body, because its buoyant force corresponds to the quantity of fuel positively displaced.
One essential advantage of such an embodiment is also that a reliable sealing function of the closing element is thus attained, even if the sealing seat is dirty, since the buoyancy of the float body increases the sealing force, and the closing element is thus sealed off even better.
The closing element is preferably embodied as a flap or umbrella valve, whose sealing function and closing function are decoupled by the fuel level-dependent positioning controlled by the float body. The term xe2x80x9cdecoupledxe2x80x9d should be understood in this context to mean on the one hand that the buildup of a static pressure from an adequately large quantity of fuel placed in the supply container does not actuate the closing element, and on the other that by the dimensioning of the float body, with the closing element already closed, as a consequence of the buoyancy of the float body located in the fuel, the sealing function of the closing element can be increased still further, if only the float body is dimensioned as large enough, thus making its buoyancy correspondingly great enough.
In further exemplary embodiments, the float body is either secured directly in the closing element or is connected to the closing element via a lever, which is supported between the closing element and the float body. A substantial advantage of a float body connected directly to the closing element is that the entire closing element is structurally especially simple and thus functions reliably, especially in a failsafe manner. The substantial advantage of a closing element in which the float body is connected to the actual closing element via a lever is that by a suitable choice of the lever length and the position of the float body, which is preferably disposed displaceably on the lever in the direction of the longitudinal axis of the lever, is that the closing moment in particular and thus the sealing force of the closing element, embodied as an umbrella valve, can be designed to be settable.
The closing element is preferably disposed on the bottom of the suction container in such a way that the umbrella of the umbrella valve is disposed on the outside of the bottom of the suction container, that is, the outside oriented toward the bottom of the supply container, while the float body is disposed in the interior of the suction container. However, it is also possible to dispose the closing element in the region of the bottom of the suction container, on its side wall, in which case the actuation of the closing element takes place via a float body connected to the closing element by a deflection lever.
Along with the use of a size of the float body adapted to the particular location and desired sealing force of the closing element, it is also possible to provide an electromagnet, for instance, as the actuating element, the electromagnet being controlled as a function of the fuel level. For detecting the fuel level, in such a case, fuel fill level sensors of a type known per se should be provided. An actuating device of this kind has the advantage that the closing element is completely decoupled from the fuel level or from the quantity of fuel introduced.